Timing of valve replacement in aortic stenosis. Clinical, diagnostic and prognostic factors of importance

Abstract

Aortic stenosis (AS) is the most common valve disorder in the adult population. Decisions relating toaortic valve replacement (AVR) are based on echocardiographic findings and the presence ofsymptoms. The timing of AVR influences both morbidity and mortality preoperatively andpostoperatively. Patients may undergo AVR at the optimal time, too early or too late. The aims of thisthesis were to investigate diagnostic, clinical and prognostic factors of importance for the timing ofAVR in AS patients.The study population originates from 678 patients who underwent AVR in 1991-1993. Preoperativeclinical and echocardiographic data were collected. Echocardiographic examinations were performedpreoperatively and two and ten years postoperatively. Mortality was recorded during the 14-yearfollow-up period. The effect of pressure recovery on stenosis severity was studied, as well as theprognostic importance of preoperative diastolic dysfunction, the importance of doctor s delay onoutcome and the long-term effect of AVR on left ventricular mass and diastolic function.The time on the waiting list for AVR significantly influenced the risk of death immediately after AVR(p=0.0083). Severe dyspnoea preoperatively independently predicted postoperative mortality (hazardratio 1.76, 95% CI 1.28-2.43, p=0.0005). Severe dyspnoea (NYHA III/IV) was present preoperativelyin 46% of patients who had been followed for more than one year prior to AVR. In 55% of thepatients, the AS was diagnosed less than one year prior to AVR, which indicates late diagnosis.Pressure recovery estimated from a previously validated equation was found in most patients withsevere AS (maximum gradient > 70mmHg). An estimated net gradient (maximum gradient pressurerecovery) of < 70 mmHg was seen in 23% of these patients. Moderate to severe diastolic dysfunctionwas identified as an independent predictor of late total mortality (hazard ratio 1.72, p=0.0038). Theprognostic importance of moderate to severe diastolic dysfunction did not diminish with time; instead,it tended to increase. In the echocardiographic follow-up, 7% showed signs of moderate to severediastolic dysfunction preoperatively. This was relatively unchanged two years postoperatively, 13%(p=0.27), but increased ten years postoperatively to 62% (p<0.0001). There was a reduction in leftventricular mass index between the preoperative (161 ± 39 g/m2) and the two-year postoperativeinvestigation (114 ± 28 g/m2), (p<0.0001), but no further regression was seen at the ten-yearinvestigation (119 ± 49 g/m2), (p=0.96).Time on the waiting list for AVR affects survival during the first postoperative months. Late diagnosisand referral for AVR is common and affects long-term survival. Severe dyspnoea preoperatively is anindependent predictor of postoperative mortality. Pressure recovery can be expected in most patientswith AS and high Doppler gradients and may explain why some patients with high Doppler gradientsare asymptomatic. Preoperative moderate to severe diastolic dysfunction is an independent predictor oflate total mortality after AVR. The development of diastolic dysfunction is seen in patients ten yearsafter AVR, despite a reduction in left ventricular mass. These findings might imply non-reversiblemyocardial structural changes.